As is well known to those skilled in the art, solid carbonaceous materials, including coals of high and low rank, may be subjected to various processes to convert at least a portion of the carbon present in the solid to a liquid form; and these processes for hydrogenation of coal are commonly termed H-coal processes.
In these processes, finely powdered coal, typically of size such that at least 100 w% passes through a 40 mesh US Standard sieve is contacted (in the form of a slurry) with hyrogen at 350.degree. C.-600.degree. C., say 450.degree. C. and 1000-2500 psig, say 2000 psig to form hydrocarbons characterized by increased hydrogen content. Illustrative of processes for upgrading coal are those disclosed in U.S. Pat. No. 2,221,886; 2,860,101; and 3,341,447.
Product hydrocarbon liquids are separated by distillation leaving a hydrophobic solid typically characterized as follows:
TABLE ______________________________________ Property Typical Value ______________________________________ w % carbon 16 density g/cc 1.4 boiling point above 1300.degree. F. Particle size 1-2 inch flakes ______________________________________
It is desirable to use this H-coal residue as a charge to a gasification reaction i.e. to convert it to a synthesis gas (containing carbon monoxide and hydrogen) by partial combustion; but this has proven to be difficult because of the problems encountered during feed preparation. The synthetic H-coal is a composition which has properties totally unlike those of other carbonaceous materials; and these render it particularly and uniquely difficult to handle.
It is found that if H-coal be subjected to grinding and mixing with water in an attempt to form a slurry suitable for use as feed to gasification, the slurry is characterized by problems which render this difficult-to-impossible.
These difficulties arise at least in part because the H-coal residues contain low melting particles or flakes admixed with particles of higher melting point. When the mix is ground, as is done to prepare it for use as feed to a coal gasification operation, it is found that the heat of grinding melts the low melting point components during grinding. The melt gums up the impact mill to a point at which it is inoperative.
It is an object of this invention to provide a process for treating a mixture containing low melting particles and high melting particles. Other objects will be apparent to those skilled in the art.